(Field of the Invention)
The present invention relates to exhaust chambers disposed in exhaust passages through which exhaust gas from engines of saddle-riding type vehicles pass.
(Description of Related Art)
It has been known that saddle-riding type vehicles such as motorcycles have exhaust chambers in exhaust passages through which exhaust gas from engines pass (for example, JP Laid-open Patent Publication No. 2009-041562). The exhaust chamber is disposed upstream of a muffler positioned at a downstream end of the exhaust passage with respect to a direction of flow of the exhaust gas. Such an exhaust chamber allows sufficient muffling effect for exhaust gas to be obtained without increasing a size of the muffler.
An exhaust chamber is generally formed so as to have a so-called “two-part structure” obtained by two divisional parts being joined to each other since the shape of the exhaust chamber is complicated in many cases. Further, in order to enhance silencing effect, it is advantageous that the exhaust chamber has a great capacity. However, when the capacity is increased, a planar portion of the outer shape tends to be increased, and vibration sound is more likely to be radiated due to vibration of the exhaust chamber.